diff --git a/src/main.cpp b/src/main.cpp
index aac8a13..f2a107f 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -38,9 +38,6 @@ std::ostream& help(std::ostream& out) {
     << "     ,--#-,\n"
     << "<3  / \\____\\  <3\n"
     << "    |_|__A_|\n"
-#ifdef _WIN32
-    << "use command <chcp 65001> to use unicode.\n"
-#endif
     << "\nnasal <option>\n"
     << "option:\n"
     << "   -h,   --help     | get help.\n"
diff --git a/test/ascii-art.nas b/test/ascii-art.nas
index 1ea8bdf..ce654a6 100644
--- a/test/ascii-art.nas
+++ b/test/ascii-art.nas
@@ -1,7 +1,7 @@
 use std.padding;
 use std.process_bar;
-use std.os;
 use std.unix;
+use std.runtime;
 
 var char_ttf=[
     ["    ","    ","    ","    ","    ","    "],
@@ -196,9 +196,7 @@ var ansi_escape_sequence = func() {
 }
 
 # enable unicode
-if (os.platform()=="windows") {
-    system("chcp 65001");
-}
+runtime.windows.set_utf8_output();
 
 trans_ttf("just for test");
 trans_ttf(" ValKmjolnir ");
diff --git a/test/coroutine.nas b/test/coroutine.nas
index deb1c1d..f0e938e 100644
--- a/test/coroutine.nas
+++ b/test/coroutine.nas
@@ -4,9 +4,10 @@ use std.coroutine;
 use std.process_bar;
 use std.padding;
 use std.os;
+use std.runtime;
 
 if (os.platform()=="windows") {
-    system("chcp 65001");
+    runtime.windows.set_utf8_output();
     system("color");
 }
 
diff --git a/test/filesystem.nas b/test/filesystem.nas
index 27d67e9..515b48f 100644
--- a/test/filesystem.nas
+++ b/test/filesystem.nas
@@ -1,4 +1,4 @@
-use std.os;
+use std.runtime;
 use std.io;
 use std.unix;
 
@@ -35,7 +35,7 @@ var prt = func(s,path) {
 }
 
 # enable unicode
-if (os.platform()=="windows")
-    system("chcp 65001");
+runtime.windows.set_utf8_output();
+
 println("\e[33m[",unix.getcwd(),"]\e[36m>\e[0m");
 prt([""],".");
\ No newline at end of file
diff --git a/test/md5compare.nas b/test/md5compare.nas
index f5cb242..c5c17fc 100644
--- a/test/md5compare.nas
+++ b/test/md5compare.nas
@@ -1,7 +1,7 @@
 use test.md5_self;
 use std.process_bar;
 use std.file;
-use std.os;
+use std.runtime;
 use std.io;
 use std.math;
 
@@ -101,8 +101,6 @@ var randomchecksum = func() {
     }
 }
 
-if (os.platform()=="windows") {
-    system("chcp 65001");
-}
+runtime.windows.set_utf8_output();
 filechecksum();
 randomchecksum();
\ No newline at end of file
diff --git a/test/occupation.nas b/test/occupation.nas
index 6774b63..ffae78b 100644
--- a/test/occupation.nas
+++ b/test/occupation.nas
@@ -11,7 +11,7 @@ var is_windows_platform=os.platform()=="windows";
 var is_macos_platform=os.platform()=="macOS";
 
 if (is_windows_platform) {
-    system("chcp 65001");
+    runtime.windows.set_utf8_output();
 }
 
 var cpu_stat = func() {
diff --git a/test/qrcode.nas b/test/qrcode.nas
index 04fb12a..8b72019 100644
--- a/test/qrcode.nas
+++ b/test/qrcode.nas
@@ -1,4 +1,5 @@
-use std.os;
+use std.runtime;
+
 var code=[
     [1,1,1,1,1,1,1,0,1,0,0,1,1,0,1,0,1,0,1,1,0,0,1,1,1,1,1,1,1],
     [1,0,0,0,0,0,1,0,0,1,1,0,0,1,0,0,0,1,1,1,1,0,1,0,0,0,0,0,1],
@@ -32,8 +33,7 @@ var code=[
 ];
 
 # enable unicode
-if (os.platform()=="windows")
-    system("chcp 65001");
+runtime.windows.set_utf8_output();
 var texture=["  ","██"];
 for(var i=0;i<size(code);i+=1) {
     for(var j=0;j<size(code[i]);j+=1)
diff --git a/test/snake.nas b/test/snake.nas
index 3a314b8..303c8f3 100644
--- a/test/snake.nas
+++ b/test/snake.nas
@@ -2,7 +2,6 @@ use module.libkey;
 use std.list;
 use std.runtime;
 use std.coroutine;
-use std.os;
 use std.unix;
 
 var game = func(x,y) {
@@ -130,8 +129,7 @@ var co=coroutine.create(func() {
 var main = func(argv) {
     var should_skip=(size(argv)!=0 and argv[0]=="--skip");
     # enable unicode
-    if (os.platform()=="windows")
-        system("chcp 65001");
+    runtime.windows.set_utf8_output();
     print("\ec");
 
     var g=game(15,10);
diff --git a/test/tetris.nas b/test/tetris.nas
index 3493c2c..571106c 100644
--- a/test/tetris.nas
+++ b/test/tetris.nas
@@ -1,6 +1,5 @@
 use module.libkey;
 use std.runtime;
-use std.os;
 use std.unix;
 
 var color=[
@@ -277,9 +276,9 @@ var mapgen = func(mapx,mapy) {
 var main = func(argv) {
     var should_skip=(size(argv)!=0 and argv[0]=="--skip");
     var init_counter=should_skip?5:30;
-    # windows use chcp 65001 to output unicode
-    if (os.platform()=="windows")
-        system("chcp 65001");
+
+    # windows use 65001 to output unicode
+    runtime.windows.set_utf8_output();
     
     print(
         "\ec\e[1:1H",
diff --git a/test/wavecollapse.nas b/test/wavecollapse.nas
index 5c34caa..cd46833 100644
--- a/test/wavecollapse.nas
+++ b/test/wavecollapse.nas
@@ -1,6 +1,6 @@
 # wave collapse function 2022/4/10
 # by ValKmjolnir
-use std.os;
+use std.runtime;
 
 srand();
 var table=[
@@ -96,8 +96,7 @@ var map = func() {
 }();
 
 # enable unicode
-if (os.platform()=="windows")
-    system("chcp 65001");
+runtime.windows.set_utf8_output();
 map.new(90);
 
 for(var iter=0;iter<40;iter+=1) {